Electrophoresis of emulsion droplets. Application of relaxation correction and liquid drop electrophoresis equations

Abstract

In some earlier publications (1, 2, 3), the relaxation correction in the theory of electrophoresis of non-conducting solid spherical particles has been considered in detail. The different analytical approximations of Overbeek (4) and Booth (5), as also the computer calculation solution of the problem by Wiersema, Loeb and Overbeek (6) (W. L. O.) were considered. It was mentioned (1, 6) that mobility data for particles of different sizes in electrolyte solutions of constant concentrations are the most suitable for this purpose, because the quantity ζ is then presumably held constant. However, such data are very meagrely recorded in literature (7–10); and, generally speaking, it has not been possible to decide conclusively regarding the relative merits of the different theoretical treatments mentioned on the basis of the results of their application to the few experimental studies cited. It was the object of the present research to undertake precise measurement of electrophoretic mobilities of droplets of varying sizes of some oil-in-water emulsions (using oils of different viscosities); to study the effect thereon of the addition of counterions of different valencies at different concentrations; and to interpret the experimental results on the basis of the different theoretical treatments mentioned with a view to be able to decide between their relative merits. Since we use in our experiments liquid droplets rather than solid particles, while applying nevertheless the theoretical relaxation correction treatments pertaining to the latter, therefore the assumption is made that the liquid droplets behave as rigid particles; the results themselves show how far this is justified.